1. Field of the Invention
This invention relates to a process and an apparatus for laying rubber materials for tire-constitutional members around a rotating support, and more particularly to a process and an apparatus for laying rubber materials for the tire-constitutional members in a high accuracy and a high efficiency.
2. Description of Related Art
The pneumatic tire (hereinafter referred to as a tire) comprises reinforcing members such as rubberized cords and the like, and various rubber members. Therefore, a green tire is provided by laying reinforcing materials such as uncured rubber materials, uncured rubberized cord materials and the like at a shaping step prior to vulcanization of the green tire.
Recently, properties required for the tire tend to become more highly developed and be more diversified and hence the tire-constructional members are more diversified in accordance with this tendency. As a result, it is obliged to make the shaping step more complicated. Therefore, it is difficult to completely automate the shaping step and a hand working is yet required in the present circumstances. However, when the hand working is used, the higher improvement of the shaping efficiency is not expected and the laying accuracy of various materials is damaged. Particularly, the laying accuracy depends the quality of the tire, so that it is strongly demanded to increase the laying accuracy together with the increase of the shaping efficiency.
In order to satisfy such demands, JP-B-7-94155 proposes a method and apparatus wherein an outlet orifice of a volumetric extruder is located near to a position for feeding a rubber material onto a rotating support and the rubber material is directly extruded on the support through the outlet orifice from the volumetric extruder.
In the method and apparatus proposed in JP-B-7-94155, it is difficult to maintain the sectional shape of a continuous extruded rubber material during the laying due to the surging or so-called change of extrusion amount inherent to the extruder when the extruded rubber material has particularly a thin gauge. And also, the following problem is caused because various rubber materials are laid on the rotating support.
Since the viscoelasticity differs in accordance with the kind of the rubber material, the die swell quantity is also changed. For this end, it is required to take means for controlling the sectional shape of the rubber material to be laid. This is attained by replacing the die with another die, or by changing the die form through some methods. In any case, such a control means takes a significant time for coping with the different die swell quantities, and also there is caused a problem of lowering the laying productivity.
It is, therefore, an object of the invention to provide a process for laying rubber materials for tire-constitutional members wherein an uncured rubber material constituting each tire-constitutional member can be laid on a rotating support in a high accuracy and a high efficiency.
It is another object of the invention to provide an apparatus capable of advantageously realizing the above process.
According to a first aspect of the invention, there is the provision of a process for laying an uncured rubber material for a tire-constitutional member on a rotating support, which comprises driving a pair of rollers located near to a surface of a radially outer portion of the rotating support in opposite directions so as to serve a gap defined between the pair of the rollers as a roller die, feeding a rubber material having a gauge larger than the gap to the roller die, and laying the rubber material fed through the roller die to the rotating support.
The term xe2x80x9crotating supportxe2x80x9d used herein means a metal core removably fitted to a shaft provided with a driving source, or a composite of the metal core and a material such as rubber material for tire-constitutional member or rubberized reinforcing cord material, a part of which being laid on a radially outer portion of the metal core.
In a preferable embodiment of the first aspect of the invention, the gap of the roller die is freely adjusted so as to adjust a sectional shape of the rubber material fed through the roller die.
In another preferable embodiment of the first aspect of the invention, an outlet port of a volumetric extruder is located in the vicinity of the roller die opposed to the vicinity of the surface of the radially outer portion of the rotating support and the rubber material is extruded from the volumetric extruder to the roller die. Moreover, a rubber strip of a high temperature may directly be fed to the roller die through hot rolls, calendar rolls or the like in stead of the volumetric extruder.
In the other preferable embodiment of the first aspect of the invention, the pair of rollers are moved around the radially outer portion of the rotating support from one side toward the other side. Thus, the rubber material is toroidally formed on the radially outer portion of the rotating support.
In a still further preferable embodiment of the first aspect of the invention, the rubber material fed through the roller die is guided by either one of the pair of rollers toward the surface of the radially outer portion of the rotating support.
In order to ensure the accuracy of the rubber material to be laid, it is favorable that a surface peripheral speed of the radially outer portion of the rotating support is made approximately equal to an outer peripheral surface speed of the roller during the laying of the rubber material onto the rotating support.
In order to surely adhere a top portion of the rubber material to the rotating support, it is favorable that the surface peripheral speed of the radially outer portion of the rotating support in the laying of a starting point of the rubber material onto the rotating support is 1.0-1.05 times the outer peripheral surface speed of the roller.
In case of using the volumetric extruder, it is favorable that the surface peripheral speed of the radially outer portion of the rotating support and the outer peripheral surface speed of the roller are made higher than an extruding rate of the rubber material from the volumetric extruder during the laying of the rubber material onto the rotating support.
In case of using the volumetric extruder, it is favorable to use a gear pump in the volumetric extruder. Thus, the surging phenomenon can be solved practically.
According to a second aspect of the invention, there is the provision of an apparatus for laying rubber materials for tire-constitutional members around a rotating support, comprising a volumetric extruder feeding an uncured rubber material onto the rotating support, a pair of rollers located near to an outlet port of the volumetric extruder and near to a radially outer portion of the rotating support and driven in opposite directions to each other, and a gap defined between the pair of the rollers and serving as a die for the rubber material to be laid.
In a preferable embodiment of the second aspect of the invention, the pair of the rollers are provided with a gap adjusting mechanism adjusting the gap of the die.
In another preferable embodiment of the second aspect of the invention, a gear pump is used in the volumetric extruder.
In the other preferable embodiment of the second aspect of the invention, the apparatus comprises a turning table fixedly supporting the volumetric extruder and the pair of the rollers, and the turning table is provided with a driving means for changing relative positions of the pair of the rollers and the volumetric extruder to a surface of the radially outer portion of the rotating support.
In a further preferable embodiment of the second aspect of the invention, the volumetric extruder is provided with a screw extruder connected to a side of an inlet port thereof, and the turning table fixedly supports the volumetric extruder through the screw extruder.
In a still further preferable embodiment of the second aspect of the invention, the turning table is provided on its lower side with a horizontally moving table, and the horizontally moving table comprises a mechanism freely moving in parallel to a rotating axial line of the rotating support and a mechanism freely moving in a direction perpendicular to the rotating axial line. Thus, it is possible to automatically move the pair of the rollers along an outer periphery of the rotating support having a toroidal shape at its outer profile section by these two tables.